A pump-passively Q-switched laser

Abstract

The application discloses a pumped passive Q-switched laser, characterized in that the pumped passive Q-switched laser comprises a pumping source (1), a laser resonant cavity (2) and a pumped light shaping and coupling device (3), wherein the laser resonant cavity (2) comprises, in sequence along an optical axis, a total reflection mirror (21), a laser gain medium, a passive Q-switched crystal (23) and an output mirror (24); the passive Q-switched crystal (23) is provided with a cooling device (4), and the cooling device (4) is used for dissipating heat of the passive Q-switched crystal (23). The application adds the cooling device (4) on the passive Q-switched crystal (23), dissipates heat of the passive Q-switched crystal (23), keeps the temperature of the passive Q-switched crystal (23), makes the passive Q-switched crystal (23) bear higher intracavity laser power density, and thus the application is applied to a high-power slab laser.

Description

Technical Field

[0001] This application relates to the technical field of lasers, and more particularly to a pumped passively Q-switched laser. Background Technology

[0002] LD-pumped passively Q-switched lasers are an important technology for obtaining high repetition rates, high peak power, and narrow pulse laser output. In low-to-medium power solid-state laser devices, passive Q-switching technology has been widely used due to its advantages such as low cost, reliable operation, and simple structure, and its applications are found in various fields such as medical, marking, fiber lasers, and ranging.

[0003] In current related technical solutions, the pump light enters the laser gain medium through a pump coupling system. The passively Q-switched laser is located behind the laser gain medium and absorbs some of the stimulated emission emitted by the laser gain medium, thereby generating laser pulse output. Because the passively Q-switched laser absorbs the stimulated emission emitted by the laser gain medium, the crystal inside the passively Q-switched laser absorbs the high power density laser, causing the temperature to rise. The crystal continuously absorbs heat and generates internal stress, which can easily lead to crystal damage. Therefore, due to heat dissipation problems, passively Q-switched lasers can mostly only be used in low-power solid-state laser devices. Summary of the Invention

[0004] (I) Purpose of the Invention

[0005] The purpose of this application is to provide a passively Q-switched laser to address the problem that existing large-size slab lasers cannot operate in a Q-switched manner. Conventional passively Q-switched lasers can only be used in low-power solid-state laser devices. By adding a cooling device to the passively Q-switched crystal to dissipate heat and maintain its temperature, the passively Q-switched crystal can withstand higher intracavity laser power densities, thus enabling its application in high-power slab lasers.

[0006] (II) Technical Solution

[0007] To address the aforementioned technical problems, this application provides a pumped passively Q-switched laser, comprising: a pump source for generating laser pump; a laser resonant cavity 2 disposed on one side of the pump source for oscillating the laser within it; and a pump light shaping and coupling device 3 located between the pump source and the laser resonant cavity 2 for shaping and coupling the high-power pump light generated by the pump source into the laser resonant cavity 2. The laser resonant cavity 2 includes a total reflection mirror 21, a laser gain medium, a passively Q-switched crystal 23, and an output mirror 24 arranged sequentially along the optical axis. A cooling device 4 is disposed on the passively Q-switched crystal 23 for dissipating heat from the passively Q-switched crystal 23.

[0008] By adopting the above technical solution, the laser generated by the pump source is shaped by the pump light shaping coupling device, and the pump light enters the laser gain medium of the laser resonant cavity. The laser oscillates between the total reflection mirror and the output mirror, and forms a Q-switched pulse laser output under the modulation of the passive Q-switched crystal. The passive Q-switched crystal is cooled by a cooling device to dissipate heat and maintain its temperature. Therefore, the passive Q-switched crystal can withstand higher intracavity laser power density and obtain higher power Q-switched laser output, thus making it applicable to high-power slab lasers.

[0009] Preferably, the cooling device includes a first microchannel heat exchanger and a second microchannel heat exchanger that are arranged opposite to each other and can be cooled by water. The passive Q-switching crystal is located between the first microchannel heat exchanger and the second microchannel heat exchanger and is clamped and fixed. The opaque side of the passive Q-switching crystal is in contact with the first microchannel heat exchanger and the second microchannel heat exchanger.

[0010] Preferably, the cooling device further includes a first heat sink for fixing the first microchannel heat exchanger and a second heat sink for fixing the second microchannel heat exchanger. The first heat sink is provided with a first water inlet pipe and a first water outlet pipe for forming a first flow channel with the microchannels of the first microchannel heat exchanger.

[0011] The second heat sink is provided with a second inlet pipe and a second outlet pipe for forming a second flow channel with the microchannels of the second microchannel heat exchanger.

[0012] Preferably, the passive Q-switching crystal is configured as a slab-like structure, and the opaque side of the passive Q-switching crystal is in contact with and fixed to the first heat sink and the second heat sink.

[0013] Preferably, the passively Q-switched crystal is a large-size saturable absorber comprising Cr:YAG, and its aperture is larger than the maximum spot size of the laser's oscillating light.

[0014] Preferably, the laser gain medium includes, but is not limited to, Nd:YAG and Yb:YAG slab crystals. The slab crystal is configured as an isosceles trapezoidal slab structure. The upper bottom surface of the slab crystal, serving as the incident surface, is coated with an antireflection film for the pump light, and the lower bottom surface is coated with a high reflectivity film for the pump light. The oscillating laser undergoes total internal reflection between the upper and lower bottom surfaces inside the slab crystal, and is transmitted in a zigzag optical path.

[0015] Preferably, the center wavelength of the pump source includes, but is not limited to, 808nm, 885nm, 940nm or 976nm.

[0016] Preferably, the center wavelength of the pump light generated by the pump source matches the absorption spectrum of the laser gain medium.

[0017] Preferably, the total reflection mirror is a curved mirror or a plane mirror, and is coated with a high-reflectivity film for oscillating light.

[0018] Preferably, the output mirror is a curved mirror or a plane mirror, with a partially transmittance film for oscillating light deposited on the side facing the laser gain medium, and a high transmittance film deposited on the other side, for coupling the laser in the output cavity.

[0019] (III) Beneficial Effects

[0020] The above-mentioned technical solution of this application has the following beneficial technical effects: It adopts a passive Q-switching crystal with a larger light-transmitting surface than conventional acousto-optic Q-switches and electro-optic Q-switches, which solves the problem that it is not easy to achieve Q-switching operation in high-power slab lasers with large light-transmitting cross-sections. At the same time, a cooling device is used to cool the passive Q-switching crystal, so that the passive Q-switching crystal dissipates heat and maintains the temperature of the passive Q-switching crystal, which solves the heat dissipation problem of large-volume passive Q-switching crystals. Therefore, it can output higher power pulsed laser. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a pumped passively Q-switched laser according to a preferred embodiment of this application;

[0022] Figure 2 This is a schematic diagram of the cooling device structure of a passive Q-switched crystal according to an exemplary embodiment of this application;

[0023] Figure 3 yes Figure 2 The longitudinal cross-section of the cooling device shown;

[0024] Figure 4 yes Figure 2 A schematic diagram of the transverse cross-section of the cooling device shown.

[0025] Figure 5 yes Figure 2 A partial structural schematic diagram of the first microchannel heat exchanger and the first heat sink in the cooling device shown.

[0026] Figure 6 This is a schematic diagram of a lath crystal according to the preferred embodiment of this application.

[0027] Figure label:

[0028] 1. Semiconductor pump light source; 2. Laser resonant cavity; 21. Total reflection mirror; 22. Slab crystal; 221. Top surface; 222. Waist; 23. Passively Q-switched crystal; 24. Output mirror; 3. Pump light shaping and coupling device; 4. Cooling device; 41. First heat sink; 411. First groove; 412. First mounting hole; 413. First water inlet pipe; 414. First water outlet pipe; 42. Second heat sink; 421. Second groove; 422. Second mounting hole; 423. Second water inlet pipe; 424. Second water outlet pipe; 43. First microchannel heat exchanger; 431. First mounting hole; 432. First cavity; 44. Second microchannel heat exchanger; 441. Second mounting hole; 442. Second cavity; 5. Bolt; 6. Metal plate. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention.

[0030] In existing technical solutions, a passively Q-switched laser includes a pump source, a pump coupling system, a laser gain medium, and a saturable absorber. The pump source emits pump light which enters the laser gain medium through the pump coupling system. The saturable absorber is placed behind the laser gain medium. The saturable absorber absorbs some of the stimulated emission emitted by the laser gain medium, generating a laser pulse output. The saturable absorber absorbs high power density laser light, causing its temperature to rise. The saturable absorber continuously absorbs heat, generating internal stress, which can easily lead to damage to the saturable absorber.

[0031] Figure 1 This is a schematic diagram of the structure of a pumped passively Q-switched laser according to an exemplary embodiment of this application.

[0032] like Figure 1 As shown, this embodiment provides a pumped passively Q-switched laser, which includes a laser resonant cavity 2 and a pump source disposed on one side of the laser resonant cavity 2. The function of the pump source is to excite the laser working medium, pumping activated particles from the ground state to a higher energy level to achieve population inversion. Depending on the working medium and laser operating conditions, different excitation methods and devices can be adopted, the most common being: optical pumping, gas discharge excitation, chemical excitation, and nuclear excitation. In this embodiment, a semiconductor pump source 1 is used as an example for illustration.

[0033] A pump light shaping and coupling device 3 is provided between the semiconductor pump source 1 and the laser resonant cavity 2 to shape and couple the high-power pump light generated by the semiconductor pump source 1 before it enters the laser resonant cavity 2. Optionally, in this embodiment, the pump light shaping and coupling device 3 is a rectangular waveguide, which shapes the pump light emitted by the semiconductor pump source 1 into a uniformly distributed rectangular spot and irradiates the laser gain medium. Alternatively, the homogenized pump light can be shaped into a spot that matches the incident surface region of the laser gain medium in the laser resonant cavity 2, maximizing the utilization of the volume of the laser gain medium.

[0034] The laser resonant cavity 2 includes a total reflection mirror 21, a laser gain medium, a passively Q-switched crystal 23, and an output mirror 24 arranged sequentially from left to right along the optical axis.

[0035] The laser generated by the semiconductor pump source 1 is shaped and coupled by the pump light shaping and coupling device 3. The shaped and coupled pump light enters the laser gain medium. The laser oscillates between the total reflection mirror 21 and the output mirror 24 in the laser resonant cavity 2, and forms a pulsed laser output under the modulation of the passive Q-switching crystal 23. The laser gain medium absorbs the pump light to store energy. At this time, since most of the electrons in the passive Q-switching crystal 23 are in the ground state, the absorption coefficient is very large. The laser is in a low Q value (i.e., high loss) state in the laser resonant cavity 2 and cannot form laser oscillation. Therefore, the radiative transition that occurs in the laser gain medium at this time is a spontaneous radiative transition, which emits fluorescence. The passive Q-switching crystal 23 absorbs this fluorescence, causing the electrons to transition from the ground state to the excited state. As the energy stored in the laser gain medium increases, so does the amount of fluorescence emitted. The passively Q-switched crystal 23 absorbs a large amount of fluorescence, causing most of its electrons to be in an excited state, thus reducing its absorption coefficient for fluorescence, a process known as "bleaching." At this point, the laser is in a high-Q state (i.e., low-loss) state in the laser resonant cavity 2, generating laser oscillation. The laser gain medium releases energy, and the laser emits a laser pulse. It is evident that the passively Q-switched crystal 23 is "bleached" by absorbing the fluorescence emitted by the laser gain medium. Spontaneous fluorescence is non-directional, and the passively Q-switched crystal 23 is only "bleached" from the small portion that generates laser radiation; that is, the passively Q-switched crystal 23 absorbs a very small portion of fluorescence and is thus "bleached." After bleaching, the absorption of the laser by the passively Q-switched crystal is very small, keeping the resonant cavity in a high-Q state and forming an oscillating output.

[0036] Figure 2 This is a schematic diagram of the cooling device structure of a passive Q-switched crystal according to an exemplary embodiment of this application;

[0037] like Figure 1 , 2As shown, a cooling device 4 is provided on the passive Q-switched crystal 23 to dissipate heat. The cooling device 4 cools the passive Q-switched crystal 23, allowing it to dissipate heat and maintain its temperature. The conventional setting is to maintain the temperature at 25 degrees Celsius, primarily to keep the temperature of the passive Q-switched crystal 23 constant and prevent it from continuously heating up after absorbing heat, which could damage the crystal. The laser gain medium itself can absorb higher pump power, resulting in a higher power density within the laser resonant cavity 2. When the passive Q-switched crystal 23 maintains a constant temperature, it can withstand a higher laser power density, thus achieving a higher-power Q-switched laser output. However, because the passive Q-switched crystal 23 absorbs heat, high-power-density laser light will cause the crystal within it to continuously absorb heat, generating internal stress and ultimately leading to damage. Therefore, heat dissipation is necessary to lower the temperature of the passive Q-switched crystal 23, thereby achieving a higher-power Q-switched laser output.

[0038] When the passively Q-switched crystal 23 is operating, the higher the pump light power, the higher the oscillation laser. If the crystal inside the passively Q-switched crystal 23 can withstand the laser power, it can output the high-pulse laser. The specific output pulse laser power is subject to experimentation, with a reference value of 500W or higher.

[0039] like Figure 1 As shown, optionally, the semiconductor pump source 1 is configured as a laser diode array, located on one side of the laser gain medium. The semiconductor pump source 1 serves as a continuous laser pump source, with a center wavelength including, but not limited to, 808 nm, 885 nm, 940 nm, or 976 nm. Furthermore, the semiconductor pump source 1 provides excitation energy to the laser gain medium, and the center wavelength of the pump light matches the absorption spectrum of the laser gain medium to achieve better absorption and higher optical efficiency. In this embodiment, the center wavelength of the pump light from the semiconductor pump source 1 is 808 nm, and the power can reach the level of hundreds of watts to tens of thousands of watts.

[0040] Optionally, the total reflection mirror 21 is a plane mirror coated with a high-reflectivity film for oscillating light; the output mirror 24 is a plane mirror with a partial transmittance film for oscillating light coated on the side facing the laser gain medium and a high transmittance film coated on the other side, used to couple the laser in the output cavity.

[0041] Figure 2 This is a schematic diagram of the cooling device structure of a passive Q-switched crystal according to an exemplary embodiment of this application;

[0042] Figure 3 yes Figure 2 The longitudinal cross-section of the cooling device shown;

[0043] Figure 4 yes Figure 2 A schematic diagram of the transverse cross-section of the cooling device shown.

[0044] Figure 5 yes Figure 2 A partial structural diagram of the first microchannel heat exchanger and the first heat sink in the cooling device shown.

[0045] like Figure 2 , 3 As shown in Figures 4 and 5, the cooling device 4 includes a first heat sink 41, a second heat sink 42, a first microchannel heat exchanger 43, and a second microchannel heat exchanger 44. The first heat sink 41 is provided with a first groove 411 adapted to the first microchannel heat exchanger 43. The first microchannel heat exchanger 43 is installed in the first groove 411. Both ends of the first microchannel heat exchanger 43 extend to be aligned with the two ends of the first heat sink 41. The two ends of the first microchannel heat exchanger 43 are provided with first mounting holes 431. The two ends of the first heat sink 41 are provided with first assembly holes 412 corresponding to the first mounting holes 431.

[0046] The second heat sink 42 is provided with a second groove 421 adapted to the second microchannel heat exchanger 44. The second microchannel heat exchanger 44 is installed in the second groove 421. The two ends of the second microchannel heat exchanger 44 extend to be aligned with the two ends of the second heat sink 42. The two ends of the second microchannel heat exchanger 44 are provided with second mounting holes 441. The two ends of the second heat sink 42 are provided with second assembly holes 422 corresponding to the second mounting holes 441.

[0047] A screw 5 is disposed between the first heat sink 41 and the second heat sink 42. The screw 5 passes through the first assembly hole 412, the first mounting hole 431, the second mounting hole 441 and the second assembly hole 422 in sequence, thereby fixing the first microchannel heat exchanger 43 and the second microchannel heat exchanger 44 together. The first microchannel heat exchanger 43 has a first cavity 432 recessed on the side facing the second microchannel heat exchanger 44, and the second microchannel heat exchanger 44 has a second cavity 442 recessed on the side facing the first microchannel heat exchanger 43. When the first microchannel heat exchanger 43 and the second microchannel heat exchanger 44 are fixed by the screw 5, the first cavity 432 and the second cavity 442 interlock to form a mounting cavity for fixing and clamping the passive Q-switching crystal 23. The opaque side of the passive Q-switching crystal 23 is fixedly clamped in the mounting cavity. Optionally, the materials selected for the first heat sink 41 and the second heat sink 42 may include gold-plated copper, oxygen-free copper, copper-tungsten alloy, aluminum, and silicon. In this embodiment, gold-plated copper is used as an example for illustration.

[0048] The first heat sink 41 is provided with a first inlet pipe 413 and a first outlet pipe 414, which together with the microchannels of the first microchannel heat exchanger 43 form a first flow channel. The second heat sink 42 is provided with a second inlet pipe 423 and a second outlet pipe 424, which together with the microchannels of the second microchannel heat exchanger 44 form a second flow channel. Cooling water enters through the first inlet pipe 413 and the second inlet pipe 423 and passes through the first flow channel and the second flow channel, carrying away the heat transferred from the passive Q-switching crystal 23 to the first microchannel heat exchanger 43 and the second microchannel heat exchanger 44. Finally, the cooled water flows out through the first outlet pipe 414 and the second outlet pipe 424, thereby achieving heat dissipation for the passive Q-switching crystal 23. The equivalent diameter of the channels in microchannel heat exchangers ranges from 10 to 1000 μm. Compared with conventional heat exchangers, microchannel heat exchangers are not only smaller in size but also have a larger heat transfer coefficient and higher heat transfer efficiency.

[0049] like Figure 1 , 2 As shown, the passive Q-switched crystal 23 is configured as a strip-shaped structure and is vertically positioned relative to the laser resonant cavity 2. The side of the passive Q-switched crystal 23 facing the laser resonant cavity 2 is the incident surface, and the side facing away from the passive Q-switched crystal 23 is the exit surface, which is used to transmit the laser. The other sides of the passive Q-switched crystal 23 are clamped and contacted by the first microchannel heat exchanger 43 and the second microchannel heat exchanger 44 for heat exchange.

[0050] Furthermore, the passively Q-switched crystal 23 is a large-size saturable absorber. A saturable absorber is an optical device with definite loss. When the incident light intensity exceeds the threshold of the saturable absorber, the optical loss decreases and the transmittance increases. When the saturable absorber is excited by a beam of light, charge carriers are pumped from the ground state to the excited state. In the strongly excited state, the ground state ions are depleted, and the excited state is partially occupied, so the absorption reaches saturation. The excited state returns to the ground state through thermal stabilization and recombination, thus enabling the absorption of photons.

[0051] Saturable absorbers include, but are not limited to, Cr:YAG, with an aperture larger than the maximum spot size of the laser's oscillation beam. The oscillation spot size of high-power slab lasers is typically greater than 2*10 mm, exceeding the aperture range of conventional Q-switching devices (generally less than 7 mm). However, the passively Q-switched crystal 23 can be grown to a very large size, with a sufficiently large aperture surface that meets the requirements of slab lasers. Its specific aperture size is determined by the cross-section of the passively Q-switched crystal 23 used. Conventional Q-switches have apertures within 7 mm, but slab laser spots are generally greater than 10 mm, making Q-switching impossible. Therefore, using a large-size passively Q-switched crystal 23 can solve the technical bottleneck of Q-switching operation in high-power lasers.

[0052] Figure 6 This is a schematic diagram of a lath crystal according to the preferred embodiment of this application.

[0053] like Figure 1 , 6 As shown, optionally, the laser gain medium includes a slab-shaped crystal 22. The slab crystal 22 is an isosceles trapezoidal slab structure with Brewster angle cut. The upper bottom surface 221 of the slab crystal 22 faces the pump light shaping and coupling device 3 as the large surface side. An anti-reflection film for the pump light is coated on the large surface side of the slab crystal 22, which can absorb the pump light and generate intracavity oscillating laser, creating conditions for output laser pulses. The lower bottom surface of the slab crystal 22 is coated with a high reflectivity film for the pump light. The two waists 222 of the slab crystal 22 are chamfered. The incident light undergoes total internal reflection between the upper bottom surface 221 and the lower bottom surface of the slab crystal 22, and follows a zigzag optical path, continuously passing through the pump light coupled from the pump light shaping and coupling device 3 in both forward and reverse directions, illuminating the pump light irradiation area of ​​the upper bottom surface 221, forming positive or negative phase changes. The superposition effect cancels out the phase changes to a certain extent, thus compensating for the thermal distortion. Specifically, the laser beam continuously refracts along a zigzag pattern inside the slab crystal 22. Preferably, the slab crystal 22 serves as the gain medium, and in this embodiment, it is an Nd:YAG crystal.

[0054] like Figure 6 As shown, optionally, a cooling device is provided on the slab crystal 22. The cooling device includes, but is not limited to, a conductive cooling device. In one specific embodiment, the conductive cooling device includes a metal plate 6. The bottom surface of the slab crystal 22 can be mechanically fixed, welded, or bonded to the metal plate 6. The heat on the slab crystal 22 can be quickly conducted to the metal plate 6 and carried away, thereby achieving the cooling operation. Preferably, the metal plate 6 is a gold-plated copper heat sink.

[0055] As described above, in the laser of the present invention, without changing the internal structure and optical device settings of the laser, and under the condition of meeting the damage threshold of the slab crystal 22, the heat generated by the passive Q-switching crystal 23 due to the absorption of oscillating light is quickly carried away by the overall water cooling method, thereby maintaining the temperature of the passive Q-switching crystal 23, solving the heat dissipation problem of the large-volume passive Q-switching crystal 23, enabling it to withstand higher intracavity laser power density and obtain higher power Q-switched laser output.

[0056] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A pumped passively Q-switched laser, characterized in that, include: Pump source, used to generate laser pump; A laser resonant cavity (2) is located on one side of the pump source and is used to generate oscillations in the laser inside it; The pump light shaping coupling device (3) is located between the pump source and the laser resonant cavity (2) and is used to shape and couple the high-power pump light generated by the pump source into the laser resonant cavity (2). The laser resonant cavity (2) includes a total reflection mirror (21), a laser gain medium, a passively Q-switched crystal (23), and an output mirror (24) arranged sequentially along the optical axis; The passive Q-switching crystal (23) is provided with a cooling device (4), which is used to dissipate heat from the passive Q-switching crystal (23). The cooling device (4) includes a first microchannel heat exchanger (43) and a second microchannel heat exchanger (44) that are arranged opposite to each other and can be cooled by water. The passive Q-switching crystal (23) is located between the first microchannel heat exchanger (43) and the second microchannel heat exchanger (44) and is clamped and fixed. The opaque side of the passive Q-switching crystal (23) is in contact with the first microchannel heat exchanger (43) and the second microchannel heat exchanger (44). The cooling device (4) further includes a first heat sink (41) for fixing the first microchannel heat exchanger (43) and a second heat sink (42) for fixing the second microchannel heat exchanger (44). The first heat sink (41) is provided with a first water inlet pipe (413) and a first water outlet pipe (414) for forming a first flow channel with the microchannels of the first microchannel heat exchanger (43). The second heat sink (42) is provided with a second inlet pipe (423) and a second outlet pipe (424) for forming a second flow channel with the microchannels of the second microchannel heat exchanger (44); The passive Q-switching crystal (23) is configured as a strip structure, and the opaque side of the passive Q-switching crystal (23) is in contact with and fixed to the first microchannel heat exchanger (43) and the second microchannel heat exchanger (44). The laser gain medium includes, but is not limited to, Nd:YAG and Yb:YAG slab crystals (22). The slab crystal (22) is configured as an isosceles trapezoidal slab structure. The upper bottom surface (221) of the slab crystal (22) is coated with an anti-reflection film for pump light as the incident surface, and the lower bottom surface is coated with a high reflectivity film for pump light. The oscillating laser forms total internal reflection between the upper bottom surface (221) and the lower bottom surface inside the slab crystal (22) and is transmitted in a zigzag optical path.

2. The laser according to claim 1, characterized in that, The passively Q-switched crystal (23) is a large-size saturable absorber comprising Cr:YAG, and its aperture is larger than the maximum spot size of the laser oscillation beam.

3. The laser according to claim 1, characterized in that, The center wavelength of the pump source includes, but is not limited to, 808nm, 885nm, 940nm, or 976nm.

4. The laser according to claim 3, characterized in that, The center wavelength of the pump light generated by the pump source matches the absorption spectrum of the laser gain medium.

5. The laser according to claim 1, characterized in that, The total reflection mirror (21) is a curved mirror or a plane mirror, and is coated with a high-reflectivity film for oscillating light.

6. The laser according to claim 1, characterized in that, The output mirror (24) is a curved mirror or a plane mirror. The side facing the laser gain medium is coated with a partial transmittance film for oscillating light, and the other side is coated with a high transmittance film for coupling the laser in the output cavity.

Images